Water is to fish what air is to man!中what air is to man是什么语法功能?

问题描述:

Water is to fish what air is to man!中what air is to man是什么语法功能?

Sth be to sth what sth be to sth.这是一个固定的句型.
..对..就如..对...
这个句子是:水对于鱼就如空气对于人(一样重要).